关键词: 母线电容, 纹波电流, 动态工况, 特征分析

Abstract: The rapid calculation and statistical characteristics of the RMS value of bus capacitor ripple current under dynamic conditions of electric vehicles is a key prerequisite for conducting its reliability assessment and design. Based on circuit theory, a calculation formula for the RMS value of bus capacitor ripple current was derived; lookup table models for motor currents i_d and i_q under different control strategies were established, and combined with the vehicle longitudinal dynamics balance equation as well as motor voltage and mechanical equations, a rapid calculation model was built with vehicle speed as input and RMS value of ripple current as output. Furthermore, the statistical characteristics of capacitor ripple current under dynamic conditions of seven urban users were analyzed. Finally, a comparative analysis of the statistical characteristics of ripple current RMS values under standard cycle conditions and typical user conditions was performed. The results indicate that there are significant differences in the statistical characteristics of ripple current under different urban user operating conditions, but overall it follows a normal distribution; The typical user operating conditions have high similarity in statistical characteristic values with WLTC operating conditions, high similarity in effective value amplitude distribution with WLTC, CLTC and other operating conditions, and similarity in effective value range frequency rainflow cycle counting with CLTC-P operating conditions. This can provide reference for the construction of load models for reliability assessment of on-board bus capacitors based on user big data working conditions.

Key words: Bus capacitance, ripple current, dynamic conditions, characteristic analysis